Moist-Electric Wallpaper for Indoor Energy Harvesting and Humidity Management

MostlyStable an hour ago | parent | next [-]

Cool concept. As they mention, more work needs to be done on long term durability, although they saw no degradation in their (very short) testing period. To me, the humidity control seems more worthwhile/useful than the power generation, although that could be a useful solution for small IoT devices like door and window sensors that don't need much power.

I like it as a proof of concept, would love to see a more serious engineering effort to demonstrate what real world costs, durability, and aesthetics might look like (if significant portions of indoor walls are going to be covered in this stuff, it needs to be able to look decent).

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jedberg 2 hours ago | parent | prev | next [-]

I've thought for a while that it would be interesting to have micro dehumidifiers on my roof that supplement my water supply from humidity.

Turn myself into a moisture farmer if you will.

But then I wonder, would it be a problem if everyone did it? Would it cause humidity to drop in a bad way?

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RobGR an hour ago | parent | next [-]

There are commercially available systems that do that now, one that seems popular in my area is https://www.aquaria.world/ .

As to your question, would it be a problem if everyone did it -- it depends obviously on your definition of "problem", but consider that most people doing this have no way to dispose of the water they take from the air except by putting it back in the air. It might increase regional power consumption, and smooth out nightly shifts in atmospheric humidity, but unless there is a new river running to the sea, the average atmospheric humidity will remain the same.

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largbae an hour ago | parent [-]

This is fun, thank you! I wonder why home HVAC units couldn't just capture the drain water to accomplish something similar for "free".

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LarsAlereon 37 minutes ago | parent [-]

The condensate water is laden with bacteria, mold spores, and pollution concentrated from the air. It can definitely be filtered and sterilized, but in water scarce environments you usually can't pull enough water from the air to be worth it.

	▲	devmor 8 minutes ago \| parent [-]
		Side-tangent, but this reminded me of the health nightmare that the incredibly common “kinetic mist” style humidifiers/vaporizers are. I think there may be a general lack of understanding to how pollution and bacteria concentrate in our daily environments.

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chris_va an hour ago | parent | prev | next [-]

oo, fermi estimate time!

Typical 50% RH at ground level is ~7g/kg air, air is roughly 1kg/m^3, so between the surface and the planetary boundary layer (let's say 1km) is about 7L of water per m^2 of surface. Moving along at ~3m/s means 21L/s passes by each meter of fence line.

PBL probably mixes after about 50km, so it takes ~5 hours to normalize after you pull out water at ~5 knot wind speed. If you want to not make a dent, means you can pull less than 1L per m^2 per hour, or about 8m^3 pear, which is about 8x the yearly requirement for farmland.

So, you can irrigate a farm and your neighbors would mostly be fine.

(math not checked)

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jawns an hour ago | parent | prev | next [-]

In humid regions, there is no practical limit that would cause any noticeable effects on the humidity of outdoor air. There is just so much water in the air that even if you were running dehumidifiers across all available land area, the air is still going to feel humid.

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roughly 38 minutes ago | parent | next [-]

The other side of that is that a big problem we're going to have moving forward is dealing with increased humidity - the climate change angle isn't just heat, heat + high humidity (the wet bulb temperature) is the actual health risk and the thing that takes a heat wave from inconvenient to a genuine crisis. Turning high humidity into drinkable water is two birds with one stone, if you do it right.

(To your point, it's almost impossible to imagine we'd be able to operate it at a scale that makes a genuine impact, but these are all chaotic systems and a couple percent here and there can compound to keep things on the right side of the phase shift.)

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jedberg an hour ago | parent | prev [-]

True but in those areas it also tends to rain a lot so it's less necessary. I'm thinking about Mediterranean and desert climates.

	▲	OneDeuxTriSeiGo 35 minutes ago \| parent [-]
		As long as the water is being locally used and locally discharged (i.e. via a drainage field) it shouldn't seriously have an impact. The water would return to the water table and either be used by plants or get wicked back into the air via capillary action from evaporation on the surface.

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NewJazz 2 hours ago | parent | prev | next [-]

It would probably depend on how you use the water. Watering plants (including via gray water systems) would mean a lot of the water would evaporate or transpirate. Flushing it down the drain means it exits the system.

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shagie an hour ago | parent | prev [-]

For non-potable use, probably. Potable use might require some more treatment checks on it. It's one thing to use it for flushing the toilet... showering might be ok. Not sure about washing dishes. Washing clothes, maybe.

And for the "the amount of times I change out 2 gallons of water from the dehumidifier in the basement in the summer"... there's a lot of moisture out there.

This is constrained by season. In the winter, its much easier to get to 0% humidity than it is in the summer.

https://tropic.ssec.wisc.edu/real-time/mtpw2/product.php?col... for the total precipitable water over North America. Through the midwest, it's in the 40-50mm range.

Consider XKCD's giant raindrop - https://what-if.xkcd.com/12/

> We’ll imagine our storm measures 100 kilometers on each side and has a high TPW content of 6 centimeters. This means the water in our rainstorm would have a volume of: 100km x 100km x 6cm = 0.6km^3

> That water would weigh 600 million tons (which happens to be about the current weight of our species). Normally, a portion of this water would fall, scattered, as rain—at most, 6 centimeters of it.

Change that to 4cm for current conditions... but that's a lot of water.

https://en.wikipedia.org/wiki/Humidity#Relationship_between_...

That has a table of how much water at different humidity and temperature combinations. It's currently about 20 °C and that gives us 15.6 g/m^3.

... but there's an awful lot of air around.

This can also be complicated if you have trees or other vegetation around. The humidity at my parents place (fairly deep in the woods in farmland) is always much higher than it is if you go to the road (or in town).

https://extension.osu.edu/about/resources/corn-sweat-and-hum...

> Some research conducted by USDA Agricultural Research Service suggests that corn can contribute between 3,500 and 5,000 gallons of water per acre to the atmosphere over the course of one to two days. A typical pool contains 18,000 - 20,000 gallons.

...

So, it's complicated. Maybe, a little bit, depends on where you are.

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t0mpr1c3 7 minutes ago | parent | prev | next [-]

vaporware

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dinkblam an hour ago | parent | prev | next [-]

> A 1596-unit array powers a wireless keyboard and simultaneously reduces indoor humidity from 38% to 32%,

isn't below 40% "bad"?

	▲	ortusdux an hour ago \| parent \| next [-]
		Depends on your region, house, and preferences: https://midwesthvacpro.com/what-should-indoor-humidity-be-a-...
	▲	Carrok an hour ago \| parent \| prev [-]
		Bad by what metric?

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bix6 2 hours ago | parent | prev | next [-]

That’s impressive humidity drop for a small panel area. Curious how big the room was.

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westurner an hour ago | parent | prev | next [-]

How to make this work with infrared wallpaper?

"Ask HN: Are there infrared wallpaper products in US markets?" (2025) https://news.ycombinator.com/item?id=45444514 :

> /? infrared wallpaper heating : https://www.google.com/search?q=infrared+wallpaper+heating

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sublinear 2 hours ago | parent | prev | next [-]

I wonder if this would get moldy.

	▲	OneDeuxTriSeiGo 27 minutes ago \| parent \| next [-]
		Mold isn't really your main concern tbh. Instead it would be Legionnaires' Disease. https://en.wikipedia.org/wiki/Legionnaires%27_disease
	▲	pdonis 2 hours ago \| parent \| prev \| next [-]
		The condensate (water vapor that gets condensed out of the air in the process of generating the electricity) has to go somewhere; if it's not properly handled, yes, I would expect mold.
	▲	westurner 41 minutes ago \| parent \| prev [-]
		Some heat pumps have built-in UV-C sanitization to prevent mold. You can install an aftermarket UVC light to sanitize to prevent mold in heat pumps, humidifiers, etc

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botanrice 2 hours ago | parent | prev [-]

very solarpunk